Assessment of thermodynamic performances for distillation columns

This study uses the results of converged mass and energy balances and exergy loss profiles by the Aspen Plus simulator to assess the thermodynamic performances of existing continuous distillation columns. Distillation is highly irreversible and energy intensive process. Such an assessment identifies the level of exergy loss due to irreversibility, the avoidable part of exergy loss, and exergy efficiency. The case studies assessed are the separation sections of methanol and vinyl chloride monomer production plants, and a 15-component two-column system. These systems contain two columns in series, which separate multicomponent feeds, produce side products, and operate with integrated process heat streams. The results show considerable exergy losses mainly in and around the feed stage, condenser, and reboiler. The estimated avoidable parts of the exergy loss profiles and the total exergy losses help in identifying possible improvements.